Drive and steering equipment for a floor conveyor

ABSTRACT

A drive and steering equipment for a floor conveyor, with a drive unit which has a driving motor, a gear and a driving wheel and which is mounted in a bearing around vertical axis in a vehicle-fixed frame of the floor conveyor, a steering motor which pivots the drive unit around the vertical axis, and a control arm, an angle sensor and a steering control equipment, which adjusts a steering angle of the driving wheel through the steering motor in accordance to the signal of the angle sensor, characterised in that the control arm is rotatably mounted in a bearing coaxially or axially parallel to the drive unit via a bearing component part, the angle sensor is attached on the bearing component part and measures the relative angle between the drive unit and the bearing component part and the steering control equipment adjusts the drive unit via the steering motor such that the relative angle becomes zero.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND OF THE INVENTION

For instance, drawbar steered floor conveyors are realised such that onesingle driving wheel is mounted in a bearing around a horizontal axis ina bolster, and the bolster in its part is pivotally suspended around avertical axis in the frame of the floor conveyor. The bolster supportsalso a driving motor for the steered wheel, which is in effectiveconnection with the driving wheel via a gear. Thus, by pivoting thedrawbar, an angular shift of the driving wheel and by that a steeringaction takes place. Usually, the control of the driving motor takesplace via control elements on the head of the drawbar. It is notnecessary to say that another control arm for the steering operation ofthe steered wheel can be provided too.

It is also known to provide a servo drive for the steering. For thispurpose, a steering motor is used, which is fixedly attached on theframe and acts on a gearwheel which is arranged concentrically to thedriving motor, via a chain for instance, in order to pivot the bolsteror the driving unit, respectively. It is also known to fix a drawbar atanother position of the vehicle frame, pivotally mounted around avertical axis, without mechanical connection to the steered wheel. Thesteering angle is taken up by a sensor, which is shifted upon a pivotalmovement of the drawbar. This signal is input as a desired value into acontrol equipment. A second sensor detects the steering angle of thesteered wheel and transmits this value as a real value to the controlequipment. With the aid of a suitable algorithm, real value and desiredvalue are compared in the control equipment and a current is providedfor the servo drive, so that the real value comes closer to the desiredvalue. When the values are equal, the servo drive is switched off.

The present invention is based on the objective to provide a compactdrive and steering equipment for drawbar-guided floor conveyors, whichis realised with particularly little expenditure. In addition, it shouldhave the property that it can readily replace conventional drive units.

BRIEF SUMMARY OF THE INVENTION

In the equipment according to the present invention, the control arm, adrawbar for instance, is rotatably mounted coaxially or axially parallelto the drive unit by means of a preferably annular bearing componentpart. Preferably, an annular bearing component part is mounted in aframe-fixed bearing ring. It is also conceivable to mount the bearingcomponent part on the drive unit. Naturally, the drive unit in its turnis rotatably mounted in the frame. In the equipment according to thepresent invention, this rotatable bearing is without stops. An anglesensor is fixed on the bearing component part, and thus is moved alongtogether with the control arm when the latter is pivoted around thevertical axis. It measures the angle relative to the drive unit. When asteering operation is initiated with the aid of the control arm, adrawbar for instance, a relative movement between the control arm withthe angle sensor and the drive unit takes place at first. This angleleads to the activation of the steering motor, and the drive unit ispivoted as long till the angle which had been temporarily createdbetween control arm and drive unit becomes zero again. With other words,there is a position control towards a difference angle of zero.

In the equipment according to the present invention, control arm anddrive unit can be mounted concentrically with respect to each other.Through this, a compact, little expensive preassembly unit is achieved,which can also replace conventional drive units interface-compatiblywithout electric lines, for example. Only one sensor is needed in theequipment according to the present invention. The sensor is transmitterand rotational angle measuring device at the same time.

Different possibilities of construction are conceivable to let sensorand drive unit co-operate. One embodiment of the present inventionprovides for this purpose that the drive unit has a concentric ring gearand the sensor has a sprocket which is in engagement with the ring gear.According to a further embodiment of the present invention, the sensorwith the sprocket is pre-tensioned in the direction of the ring gear bymeans of a spring, in order to realise a tolerance compensation and aclearance-free tooth engagement. It is not necessary to say that thering gear does not have to be closed, instead a tooth segment the radiusof which passes through the rotational axis of the drive unit issufficient.

In the case that the electric supply of the servo steering fails, afurther embodiment of the present invention provides that stops areprovided on the drive unit in angular distance to both sides of the zeroposition of the control arm, against which the drawbar or its bearingcomponent part, respectively, knocks when the drawbar is pivoted aboutthe angular distance with respect to the drive unit. In this way anemergency steering ability is achieved, even though with a slip error.The difference angle between the zero position of the drawbar and thestops is at about 20°, for instance.

As a rotational angle sensor, a contactless magnetic rotational anglesensor can be provided, for instance, which creates separate analoguesignals for the sinus and the cosinus part of the measured angle. Such asensor has become known from EP 1 053 182 A1, for instance, the entirecontents of which is incorporated herein by reference. From EP 1 508 783A1, the entire contents of which is incorporated herein by reference, ithas also become known to use the sinus and the cosinus part of arotational angle sensor for the calculation of the rotational angle andto perform a temperature correction at the same time. By storing idealvalues of the output signals in an evaluation unit, which result fromthe geometrical relation of the sensors, and by comparing the measuredoutput signals with the ideal values, a warning or stopping signal canbe created, when the difference between measured and ideal value reachesa predetermined amount. In this way it is possible to monitor erroneousfunctions of the sensor in an efficient manner.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be explained in more detail by means ofdrawings in the following.

FIG. 1 shows the side view of a drive and steering unit according to theinvention,

FIG. 2 shows the side view of the drive and steering unit according tothe invention, twisted about 90° with respect to FIG. 1,

FIG. 3 shows the rear view of the equipment according to FIG. 1.

FIG. 4 shows the view under the equipment according to FIG. 1 fromunderneath, in the direction of the arrows 4.

FIG. 5 shows the top view on the equipment according to FIG. 1, in thedirection of the arrow 5.

FIG. 6 shows a partial section through the equipment according to FIG.1, along the line 6-6.

FIG. 7 shows very schematically the steering control of the equipmentshown in FIGS. 1 to 5.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein a specific preferred embodiment of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiment illustrated

In FIGS. 1, 2 and 3, a driving wheel 10 of a drawbar-steered floorconveyor is shown, which is single-sided mounted on a leg 12. In the leg12, there is a gear (not shown), which is fixedly coupled with theoutput shaft of a motor 16, of which a casing 18 is represented in FIGS.1 to 3. The leg 12 is attached on a horizontal plate 20, which is inturn connected with the casing 18 through screw bolts 22 (FIG. 6). Aninner bearing ring 24 is fixedly connected with these parts, whichco-operates via a roller bearing 26 with an outer ring 28, which isfixedly attached in the not shown frame of the not shown floor conveyor.In this way, motor casing 18 and wheel 10 can pivot around a verticalaxis, which extends through the axis of the motor 16 and through thecentre of the wheel 10. Via a series of bolts 30, the frame-fixed ring28 is connected with an upper frame-fixed ring 32, which has an innerring 24, by means of a roller bearing 34. As can be recognised in FIG.4, a ring gear or gearwheel 38 is splinedly connected with the same,around which a chain 40 is wound in a loop. The chain is also woundaround a sprocket 42, which is in turn fixed on the driving shaft of asteering motor 44. When the steering motor is actuated, it pivots thedriving wheel 10 and the motor 16 around a vertical axis into one or theother direction, depending on the rotational direction of the steeringmotor 44. The steering motor 44 is flange-connected with the frame-fixedring 32 by means of a plate 46.

A bearing component part 50 has two arms 52, 54 (FIG. 5) with oneopening 56 each at a time for the articulation of a not shown drawbar.Thus, the drawbar is pivotally mounted in a bearing around a horizontalaxis. The bearing component part 50 is connected with the inner bearingring 36. Thus, the drawbar is pivotally mounted in a bearing around thevertical axis.

On the perimeter of the casing 18 of the motor 16, a tooth segment 60 isfixed, the radius of which runs through the vertical axis. As can berecognised from FIG. 5, the tooth segment 60 is offset about an angle ofabout 90° with respect to the bearing component part 50. On the ring 36,a lever 62 is pivotally mounted, in which a sprocket 64 is rotatablymounted, which meshes with the tooth segment 60. A spring 65 (shownschematically in FIG. 7) pre-tensions the sprocket 64 against the toothsegment 60.

The sprocket 64 actuates a sensor 68, a magnetic contactless rotationalangle sensor in particular, as has been already described above. Whenthe drawbar and with it the bearing component part 50 is pivoted about acertain angle around the vertical axis of the described equipment withthe aid of the bearing ring 36, the rotational angle sensor is shiftedabout a certain angle amount via the tooth segment 60 and the sprocket64. In FIG. 7, the drawbar is indicated at 70 and the sensor at 68. Thesensor gives its signal to a control equipment 72. The control equipment72 is dimensioned such that it wants the measured angle to become zeroby triggering the steering motor 44. Thus, it actuates the unit of motorand driving wheel 10 through the described driving connection, as longtill the angle has reached zero. The measurement of the control process,i.e. the resetting of the relative angle between drawbar 70 and motorunit is on the other hand detected by sensor 68. In other words, withits signal the sensor 68 parameterizes continuously the desired value,which is always made to be zero via the steering motor 44 by actuation.In this way, an electrically controlled and actuated follow-up controlfor the steering of the wheel 10 is obtained.

In FIG. 5, stops can be recognised at 74 and 76, which are connectedwith the casing 18. Parts of the inner bearing ring 36 co-operate withthese stops in order to realise an emergency steering. In the case offailure of the electric supply, the drive unit and with it the wheel 10can be pivoted through co-operation of the drawbar with the stops 74,76, wherein a dead path has to be overcome via a slip angle at first.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the claims where the term“comprising” means “including, but not limited to”. Those familiar withthe art may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims.

Further, the particular features presented in the dependent claims canbe combined with each other in other manners within the scope of theinvention such that the invention should be recognized as alsospecifically directed to other embodiments having any other possiblecombination of the features of the dependent claims. For instance, forpurposes of claim publication, any dependent claim which follows shouldbe taken as alternatively written in a multiple dependent form from allprior claims which possess all antecedents referenced in such dependentclaim if such multiple dependent format is an accepted format within thejurisdiction (e.g. each claim depending directly from claim 1 should bealternatively taken as depending from all previous claims). Injurisdictions where multiple dependent claim formats are restricted, thefollowing dependent claims should each be also taken as alternativelywritten in each singly dependent claim format which creates a dependencyfrom a prior antecedent-possessing claim other than the specific claimlisted in such dependent claim below.

This completes the description of the preferred and alternateembodiments of the invention. Those skilled in the art may recognizeother equivalents to the specific embodiment described herein whichequivalents are intended to be encompassed by the claims attachedhereto.

1. A drive and steering equipment for a floor conveyor, with a driveunit which has a driving motor, a gear and a driving wheel and which ismounted in a bearing around a vertical axis in a vehicle-fixed frame ofthe floor conveyor, a steering motor which pivots the drive unit aroundthe vertical axis, and a drawbar, an angle sensor and a steering controlequipment, which adjusts a steering angle of the driving wheel throughthe steering motor in accordance with the signal of the angle sensor,characterised in that the drawbar is rotatably mounted in a bearingcoaxially or axially parallel to the drive unit by means of a bearingcomponent part (50), the angle sensor (68) is attached on the bearingcomponent part (50) and the steering control equipment (72) adjusts thedrive unit via the steering motor (44); further wherein the bearingcomponent part (50) is circular and rotatably mounted coaxially to thedrive unit; further wherein the bearing component part (50) is rotatablymounted in a frame-fixed bearing ring (32); further wherein the driveunit has a tooth segment (60) and the sensor (68) has a sprocket (64),which is in engagement with the tooth segment (60), and further whereinthat the sensor (68) with the sprocket (64) is pre-tensioned in thedirection of the tooth segment (60) by means of a spring.
 2. Anequipment according to claim 1, characterised in that stops (74, 76) areprovided on the drive unit in angular distance to both sides of a zeroposition of the drawbar, against which the drawbar or the drawbar'sbearing component part, respectively, knocks when the drawbar is pivotedabout the angular distance with respect to the drive unit.
 3. Anequipment according to claim 1, characterised in that a contactlessmagnetic rotational angle sensor is provided, which creates separateanalogue signals for a sine and a cosine part of a measured angle.
 4. Anequipment according to claim 1, characterised in that the controlequipment (72) generates an output signal of the angle sensor (68) whena difference between a measured and an ideal value reaches apredetermined amount.